Detinning



W. C. ZACHARIAS.

DETINNING.

APPLICATION FILED AUG.16, I919.

Patented Dec. 14, 1920.

FIELZ INVENTOR WC WALTHER C. ZACHARIAS, OF PITTSBURGH,

PENNSYLVANIA, AssreNon To' STEEL WORKS ArPLIANcEs'ooMPANY, or PITTSBURGH, PENNSYLVANIA, A comm- RATION OF PENNSYLVANIA.

DETINNING.

To all whom it may concern: I

Be it known that I, WALTHER C. ZACHA RIAS, residing at Pittsburgh, in the county of Alleghen and State of Pennsylvania, a citizen of ermany, have invented or discovered certain new and useful Improvements in Detinning, of which improvements the following is a specification.

The methods employed or suggested for detinning tin scrap or other tin coated ma terial have been either chemical or mechanical. In the practice of the chemical methods the tin is transformed generally by employment of a chemical solvent to a metallic salt which is dissolved in the solution and the tin recovered by suitable treatment of,

the solution or the salt sold as such. This method is effective but is objectionable in practice. The mechanical methods which have been suggested or tried involve the heating of the coated material above the melting point of tin and either permitting the tin to drop off or subjecting the heated material to mechanical treatment as scrap ing, agitation or by centrifugal action to dislodge the molten metal. These mechanical methods have been found to be commercially ineffective as the adherence of the tin to the other metal is so great that only what might be termed the surplus of tin is removed, a thin film of tin remaining on the metal article, and as the original coating is generally very thin, the amount recovered by known mechanical methods is too small to justify the expense involved in such treatment.

The invention described herein has for its object the transformation of the tin to such a structural condition that it can be readily detached from the surface of the other metal, by mechanical treatment as vlbration, impact, etc. In general terms, the invention consists in heating the coated articles and then subjecting the articles while heated, to blows, vibrations, or other mechanicallyapplie'd stresses whereby the tin is reduced to a powdery, condition and dislodged from the metal surfaces. The invention is hereinafter more fully described and claimed.

In the accompanying drawings forming a part of this specification, Figure 1 is a top plan view of to the practice of the invention described Specification of Letters Patent.

Application filed August 16, 1919.

a form of apparatus adapted Patented'Dec. 14, 1920. Serial No. 317,976.

herein and Fig. 2 is a sectional elevation of the same.

In the practice of the invention the material to be treated, i. e., sheets or portions of sheets or other forms or shapes of iron, steel, or other metal coated with tin are heated by any suitable means or in any suitable manner to a temperature at which the tin will become brittle and can be broken up and pulverized and detached from the surfaces of the sheets or other articles by impact or vibration. In its natural state and at normal temperature tin 1s malleable and mechanically shaped, but when heated to or above one hundred and slxty (160) degrees C. more or less, the structure of the tin is changed andthe tin becomes brittle. This brittleness increases as the temperature is raised, being substantially proportional to the increase in tem-' perature until the melting point is reached.

The brittleness is such that if the coatedmaterial is subjected while at a temperature above that at which begms, to suddenly applied stresses, as

blows or flexures or vibrations, the tin will be disintegrated and detached from the sllI'-,

faces of the sheets, etc. By the combined heat and mechanical treatment, the tin on the sheets or other articles will be reduced to a powdery condition and separated from the other metal.

As tin will oxidize more or less readily when heated, the above described treatment should, if recovery of metallic tin is desired, be carried out in a reducing or nonoxidizing atmosphere, or if tin oxid is de sired then the operation may be carried out in an oxidizing atmosphere.

It is believed that the disintegration and detachment of the tin from the sheets can be most effectively accomplished at the time when the structure of the metal is being changed by the heat, and the metal is about to assume a molten or semi-molten condition. The change or disintegration due to heat will begin at or about a temperature of 160 degrees C. and increasing with the temperature will be most efiicient at the the change in structure temperature where the bond between the vent the temperature passing above the melting point, the tin-which has been detached'is liable at times to be remelted especially when the treatment is carried out in a reducing or non-oxid1z1 atmosphere. Hence in the practice ofthe invention, the

material should be heated toa temperature V as stated, and then when necessary. cooled down to a,point below that at which any' adherence of the detached tin or soldering together of the scrapsor pieces of metal could occur, the mechanical treatment for the disintegration and detachment, of the tin being maintained during the heating and cooling operations, thereby disintegrating any tin' which has resolidified' and ad'- hered to the other-metal pieces.

While themethod herein described is not limited to the employment of any particular construction of apparatus for carrying out the method, that shown is suitable for the frame and adapted to be driven. by any suitable means, asfor example, the motor 10.

While any suitable means may be employed for turning the frame 4 on its trunnions for the purpose of discharging the contents of the drum 1, that shown is suitable and consists of a fluid pressure cylinder 11 having itspiston rod 12 connected by a link 13 to the frame 4. Any suitable means such; as the gas burners 14 may be employed for heating the drum and its contents.

1 In carrying out the method, the material to be treated, as for example the scrap, is

' in a ball mill. The removable cover is charged in suitable quantities into the drum in which are also placed metal balls of suitable/size such for example as are employed then secured in position and the drum rotated until the detinning has been'efi'ected.

The shaft 4 is provided with a passage l lthroughwhich an unoxidized or an' oxidized gas may be introduced if desired.

After the treatment has been completed the motor 10 is stopped and the fluid pressure cylinder operated, to tip the frame and the drum to an angular position as indicated for the discharge of the material.

I claim herein as my invention:

1. The method herein described of removing tin from coated articles which consists in heating the coated articles to a temperature at which the coating material will be friable and. subjecting the articles while heated to such mechanical treatment as willeffect the disintegration and consequent detachment of the tin. t I 2. The method herein describedof removing tin from coated articles which consists in heat-ing the, coated articles to a temperature at which the coating material will be friable, subjecting the articles while heated to such mechanical treatment as will effect the disintegration of the tin and its separation from the surfaces of the articles, cooling the -materials to a point substantially be.- low the melting point and maintaining the mechanical treatment during the cooling operation.

3. The-methodherein described of removing tin from coated articles which consists in heating the coated articles to the melting point of tin, subjecting the articles while being heated to such mechanical treatment as will effect the disintegration of the tin and its separation from the surfaces, of the articles, cooling the materials to a point substantially'below the melting point and maintaining the mechanical treatment during the; cooling operation and protecting the material from oxidation while heated.

In testimony whereof, I have hereunto set my hand.

1 WALTI -IER C. ZACHARIAS. 

